These unnamed children are the sons of Michael Hofstadter and his wife.
They are first mentioned in "The Celebration Reverberation" when Leonard says that if the Christmas card has a picture of his wife, children, dogs and horses all in matching pajamas, he begs Penny to burn the letter.
They are brought up again in "The Procreation Calculation", when Leonard suggests that he may be the last of the Hofstadter line (after learning Penny doesn't want kids), Sheldon reminds him of his brother Michael, as well as his sister having kids. Hearing this, Leonard sees it doesn't matter if he has kids since his siblings' children will carry on the family line.
Family
- Father: Michael Hofstadter
- Mother: Unnamed
- Uncles: Leonard Hofstadter, Unnamed
- Aunts: Unnamed, Penny
- Cousins once removed: Unnamed
- Grandfather: Alfred Hofstadter
- Grandmother: Beverly Hofstadter
- Great-grandfather: Unnamed
- Great-grandmother: Unnamed
- Great-uncles: Floyd Hofstadter, Unnamed
- Great-aunts: Edna, Nancy Hofstadter, Unnamed